The expert level AI will always win or tie on a 3x3 or 3x3x3 game if it goes first, and, while a 4x4x4 game has been mathematically solved, the AI doesn't employ the algorithm, so you can still win if you're the second player.

This was pre-loaded on my family's Packard Bell 386SX computer, and I played it a little in 1991. At 11-years-old, I could always beat or tie the AI in the 3x3 mode at any difficulty, but I was rarely able to beat the AI on 3x3x3 or 4x4x4, even on beginner difficulty, so I didn't play it much. Years later, in 2018, I tried again and was finally able to beat the AI on expert mode on the 3x3x3 and 4x4x4 boards, provided I got first move.